Display screen or portion thereof with an icon



FIG. 1 is a front view of an embodiment of a display screen or a portion thereof with an icon; and,

FIG. 2 is a front view of a second embodiment thereof.

The uneven broken line showing of the display screen or portion thereof forms no part of the claimed design. The lighter gray features between icon and the broken line showing of a display screen or portion thereof form no part of the claimed design. The small dot in FIG. 1 is lined for the color green. The small dot in FIG. 2 is lined for the color yellow. 

CLAIM The ornamental design for a display screen or portion thereof with an icon, as shown and described. 